Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “gluons”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Incoherent diffractive dijet production and gluon Bose enhancement in the nuclear wave function

We investigate the effect of gluon Bose enhancement in the nuclear wave function on the dijet production in incoherent diffractive processes in DIS and ultraperipheral collisions. We demonstrate that Bose enhancement leads to an enhancement of diffractive dijet production cross section when the transverse momenta of the two jets are aligned at zero relative angle. This enhancement is maximal when the magnitude of the transverse momenta of the two jets are equal, and disappears rather quickly as a function of the ratio of the two momenta. We study both the dilute limit and fully nonlinear dense regime where the nuclear wave function is evolved with the leading order JIMWLK equation. In both cases we observe a visible effect, with it being enhanced by the evolution due to the dynamical generation of the color neutralization scale.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Towards a general subtraction formula for NNLO QCD corrections to processes at hadron colliders: final states with quarks and gluons

We describe the calculation of integrated subtraction terms in the nested soft-collinear subtraction scheme for hadron collider processes with quarks and gluons, thereby extending the results presented in ref. [1]. Although this extension eventually proves to be straightforward, it requires a more careful treatment of certain collinear limits to achieve a compact and physically-transparent final result. We also show that the cancellation of infrared divergences can be organized in such a way that, once soft contributions are removed, it occurs independently for each of the external partons. We consider these results to be important stepping stones on the way to deriving finite remainders of the integrated subtraction terms for fully-general hadron collider processes in the context of the nested soft-collinear subtraction scheme.

NNLO calculations↗
DOE OSTI2026

A new effective field theory for heavy quarks in the quark-gluon plasma

A bstract An effective field theory framework is developed to study the interaction of heavy quarks in strongly coupled quark-gluon plasma (QGP). The latter is treated as a relativistic non-dissipative colorless fluid which can be studied using a derivatively coupled effective field theory based on previous work. Coupling this to heavy quarks provides a systematic way to obtain the interaction between the heavy quark and phonons, excitations of the fluid. In particular we calculate the quasiparticle width of heavy quark to phonon and phonon-heavy quark scattering in a thermal medium.

Kirchner, Andreas [Duke University] (ORCID:0000000↗
DOE OSTI2024

Low and moderate x gluon contribution to exclusive Compton scattering processes

We revisit the high energy semi-classical description of the exclusive processes DVCS, TCS, and Double DVCS by explicitly keeping track of the Feynman x dependence in both the hard and the hadronic matrix elements. This is achieved by a modification of the standard shock wave approximation to derive the effective Feynman rules, which leads to a generic expression on which we then perform a partial twist expansion to get rid of quantities suppressed by the proper physical scales. We obtain a compact factorized master formula that can be used to investigate the Bjorken limit at leading twist. In particular, we recover the full one-loop result in the collinear limit for pure gluon exchange with the target. Finally, we discuss the subtleties in taking the simultaneous collinear and small x limit.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Transverse single-spin asymmetries in $γ$ SIDIS as a direct probe of quark-gluon-quark longitudinal momentum structure

Transverse single-spin asymmetries in the semi-inclusive deep-inelastic production of isolated photons ($\gamma$SIDIS), $A_{UT}^{\gamma {\rm SIDIS}}$, provide an unprecedented opportunity to extract the quark-gluon-quark correlators $F_{FT}(x,x')$ and $G_{FT}(x,x')$ point-by-point in their full support $x,x'$. We utilize realistic models for these functions, based on input from the Sivers transverse momentum dependent parton distribution function and imposing constraints from the $d_2$ matrix element calculated in lattice QCD, in order to provide numerical estimates for $A_{UT}^{\gamma {\rm SIDIS}}$ at the Electron-Ion Collider (EIC). We thoroughly explore the EIC phase space in order to isolate in which regions the asymmetry can be sizable, finding it can be as much as $10\%$ or larger for certain kinematics. Given that $F_{FT}(x,x')$ and $G_{FT}(x,x')$ are basically unknown, $A_{UT}^{\gamma {\rm SIDIS}}$ will be an important future measurement to learn about multi-parton correlations in the nucleon.

Electron-Ion Collider↗
DOE OSTI2025

Simulating Charm Quarks in IP-Glasma Initial Stage and Quark-Gluon Plasma: A Hybrid Approach for charm quark phenomenology

We present phenomenological findings on charm quark transport while including its energy loss in both pre-equilibrium and hydrodynamic stages of the evolution. We employed the MARTINI event generator for the production and evolution of heavy quarks in the relativistic heavy-ion collisions. The sensitivity of the heavy meson nuclear modification factor and flow coeffcient to the early stage of heavy-ion collisions and bulk medium evolution is analyzed for Pb+Pb collisions at 5.02 TeV. Our study provides insights into the interaction strength of charm quarks during the early phase and within the quark-gluon plasma.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Rosenbluth-like separation of the $J/ψ$ near-threshold photoproduction: An access to the gluon gravitational form factors at high t

Here, we perform analysis of the near-threshold $J/\psi $ photoproduction data off the proton based on two theoretical approaches, GPD \cite{Guo3} and holographic \cite{Zahed2}, that represent the differential cross sections as powers of the skewness parameter with coefficients that depend only on the momentum transfer $t$. This allows to separate kinematically the corresponding coefficient functions, in much the same way as this is done for the electric and magnetic form factors using the Rosenbluth separation. We examine the independence of the extracted functions with the photon beam energy. These functions, under additional assumptions, are related to the proton's gluon Gravitational Form Factors (gGFFs). We compare the extracted functions with lattice calculations of the gGFFs in the region of $0.5<|t|<2$~GeV$^{2}$, where they overlap. Such analysis demonstrates the possibility of extracting some combinations of the gGFFs from the data at high $t$, complementary to the lattice calculations available in the low $t$ region. However, higher statistics are needed to more accurately check the predicted scaling behavior of the data and compare with the lattice results, thus testing and comparing the theoretical assumptions used in the GPD and holographic models.

Pentchev, Lubomir [Thomas Jefferson National Accel↗
DOE OSTI2024

Covariant formulation of spinodal decomposition in rapidly expanding quark gluon plasma

Quantum chromodynamics (QCD) is expected to have a first order phase transition between the confined hadron gas and the deconfined quark gluon plasma at high baryon densities. This will result in phase boundary effects in the metastable and unstable regions. It is important to include these effects in phenomenological models of heavy ion collisions to identify experimental signatures of a phase transition. This requires building intuition on phase separation in rapidly expanding fluids. In this work we present the covariant equations of relativistic hydrodynamics with a phase boundary, provide prescriptions to extend the equation of state to metastable and unstable regions, and show the effects of spinodal separation in a Bjorken flow. Published by the American Physical Society 2024

Kapusta, Joseph I. (ORCID:0000000259429835)↗
DOE OSTI2024

Modification of Quark-Gluon Distributions in Nuclei by Correlated Nucleon Pairs

We extend the QCD Parton Model analysis using a factorized nuclear structure model incorporating individual nucleons and pairs of correlated nucleons. Our analysis of high-energy data from lepton deep-inelastic scattering, Drell-Yan, and W and Z boson production simultaneously extracts the universal effective distribution of quarks and gluons inside correlated nucleon pairs, and their nucleus-specific fractions. Such successful extraction of these universal distributions marks a significant advance in our understanding of nuclear structure properties connecting nucleon- and parton-level quantities. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Quadrupole forces between quark and gluon subsystems inside higher-spin particles

We generalize the mechanical interpretation of the forces between quark and gluon subsystems, previously studied for the nucleon, to arbitrary higher-spin particles. For spin-0 and spin-1/2 particles, this force is characterized by the nonconserved $\overline{𝑐}$⁡(𝑡) form factor. However, such an interpretation has not yet been established for higher-spin particles due to the intricate structure of the nonconserved energy-momentum tensor (EMT) form factors. By performing a multipole expansion, we identify the physically meaningful combinations of the nonconserved covariant EMT form factors and provide them with a clear mechanical interpretation.

Baryons↗
DOE OSTI2025

Revisiting the gluon density from the Balitsky-Kovchegov equation with kinematical constraints and large 𝑥 terms

We perform analysis of the small 𝑥 nonlinear evolution equation formulated in momentum space supplemented by higher order terms. The equation is defined in the wide range of transverse momentum and longitudinal momentum fractions extending previous studies performed in Kutak and Kwiecinski [Screening effects in the ultrahigh-energy neutrino interactions, Eur. Phys. J. C 29, 521 (2003).] and in Kutak and Stasto [Unintegrated gluon distribution from modified BK equation, Eur. Phys. J. C 41, 343 (2005).]. The linear part of the equation is motivated by the renormalization group improved small 𝑥 approach, which accounts for resummation of higher orders, and includes collinear splitting functions and kinematical constraints. The solution to the equation is then used to perform the fit to deep inelastic scattering reduced cross section data.

Perturbative QCD↗
DOE OSTI2026

Regularization prescription for the mixing between nonlocal gluon and quark operators

It is well known that in the study of mixing between nonlocal gluon and quark bilinear operators there exists an ambiguity when relating coordinate space and momentum space results. In this work, we show that this ambiguity is due to the lack of a proper regularization prescription of the singularity that arises when the separation between the gluon/quark fields approaches zero. We then demonstrate that dimensional regularization resolves this issue and yields consistent results in both coordinate and momentum space. This prescription is also compatible with lattice extractions of parton distributions from nonlocal operators.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

$$\Lambda $$ polarization in very high energy heavy ion collisions as a probe of the quark–gluon plasma formation and properties

Abstract We have studied the spin polarization of $$\Lambda $$ Λ hyperons in heavy ion collisions at center-of-mass energies $$\sqrt{s_\textrm{NN}}= 200$$ s NN = 200 GeV and $$\sqrt{s_\textrm{NN}}= 5.02$$ s NN = 5.02 TeV carried out at RHIC and LHC colliders. We have calculated the mean spin vector at local thermodynamic equilibrium, including all known first-order terms in the gradients of the thermo-hydrodynamic fields, assuming that the hadronization hypersurface has a uniform temperature. We have also included the feed-down contributions to the polarization of $$\Lambda $$ Λ stemming from the decays of polarized $$\Sigma ^*$$ Σ ∗ and $$\Sigma ^0$$ Σ 0 hyperons. The obtained results are in good agreement with the data. In general, the component of the spin vector along the global angular momentum, orthogonal to the reaction plane, shows strong sensitivity to the initial longitudinal flow velocity. Furthermore, the longitudinal component of the spin vector turns out to be very sensitive to the bulk viscosity of the plasma at the highest LHC energy. Therefore, the azimuthal dependence of spin polarization can effectively constrain the initial hydrodynamic conditions and the transport coefficients of the quark gluon plasma.

Physics↗
DOE OSTI2025

Search for pair production of heavy particles decaying to a top quark and a gluon in the lepton+jets final state in proton–proton collisions at $\sqrt{s}=13\,\text {Te}\hspace{-.08em}\text {V}$

A search is presented for the pair production of new heavy resonances, each decaying into a top quark (t) or antiquark and a gluon (g). The analysis uses data recorded with the CMS detector from proton–proton collisions at a center-of-mass energy of 13 TeV at the LHC, corresponding to an integrated luminosity of 138 fb -1 . Events with one muon or electron, multiple jets, and missing transverse momentum are selected. After using a deep neural network to enrich the data sample with signal-like events, distributions in the scalar sum of the transverse momenta of all reconstructed objects are analyzed in the search for a signal. No significant deviations from the standard model prediction are found. Upper limits at 95% confidence level are set on the product of cross section and branching fraction squared for the pair production of excited top quarks in the t* → tg decay channel. The upper limits range from 120 to 0.8 fb for a t* with spin-1/2 and from 15 to 1.0 fb for a t* with spin-3/2. These correspond to mass exclusion limits up to 1050 and 1700 GeV for spin-1/2 and spin-3/2 t* particles, respectively. These are the most stringent limits to date on the existence of t* → tg resonances.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1989

One-jet inclusive cross section at order a(s)-cubed - Gluons only

A complete calculation of the hadron jet cross-section at one order beyond the Born approximation is performed for the simplified case in which there are only gluons. The general structure of the differences from the lowest-order cross-section are described. This step allows two important improvements in the understanding of the theoretical hadron jet cross-section: first, the cross section at this order displays explicit dependence on the jet cone size, so that explicit account can be taken of the differences in jet definitions employed by different experiments; second, the magnitude of the uncertainty of the theoretical cross-section due to the arbitrary choice of the factorization scale has been reduced by a factor of two to three.

Ellis, Stephen D.↗
NASA NTRS1993

Squeezed colour states in gluon jet

The possibility of the formation of squeezed states of gluon fields in quantum chromodynamics due to nonlinear nonperturbative self interaction during jet evolution in the process of e(+)e(-) annihilation into hadrons, which are analogous to the quantum photon squeezed states in quantum electrodynamics, is demonstrated. Additionally, the squeezing parameters are calculated.

Kilin, S. YA.↗
DOE OSTI2025

Lattice study of correlators of chromoelectric fields for heavy quarkonium dynamics in the quark-gluon plasma

We perform a lattice calculation of the correlators of two chromoelectric fields in the adjoint representation connected by adjoint Wilson lines at nonzero temperature. These correlators arise in the study of quarkonium dynamics and of adjoint heavy quark diffusion in deconfined matter. We work in SU(3) gauge theory using either gradient flow or multilevel algorithms for noise reduction, and discuss the renormalization of the correlators on the lattice. We find that a Casimir factor rescaling relates the adjoint correlators corresponding to the diffusion of an adjoint heavy quark and the octet-octet quarkonium transitions to the chromoelectric correlator in the fundamental representation describing the diffusion of a heavy quark.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗